1. Field of Invention
The present invention relates to ink jet printing apparatus wherein a plurality of readily insertable print/cartridges cooperate in producing a print and more particularly to a detection system for use in achieving accurate dot placements that are precisely interrelated horizontally.
2. Description of Background Art
There are known drop-on-demand ink jet printer systems in which a print head carriage bearing a print head traverses across the width of a print medium in line printing operation. Between line printing sequences, the print medium is advanced to prepare for the next sequence. One useful approach for such printing systems is to construct the print head element as part of a disposable print/cartridge which contains an ink supply, drop-generating structures and electrical connections adapted for coupling to the printer, which provides drop-generating energy to such an inserted print/cartridge.
Heretofore, such disposable print/cartridge units have been employed one unit at a time in the printing operation and precise positioning and control of the print/cartridge's printing line locus, relative to the print medium is not required. That is, a particular print/cartridge, once inserted, will establish its particular line locus vis-a-vis the printer's print zone. Thus, variation of line locus between different print/cartridges (e.g. because of low tolerances within the print/cartridge and in the print/cartridge-printer interface) has not presented problems.
However, there exist applications where it would be desirable to use a plurality of such readily insertable print/cartridges, cooperatively, in page-printing. For example, it may be desired to print more than one color of ink on a printed page. Or, it may be desired to use a plurality of cooperative print/cartridges to increase the page-printing speed of the printer. In using more than one print/cartridge for cooperative printing on a single page, it is desirable to precisely interrelate the printing loci of those print/cartridges. Otherwise printing artifacts can occur, e.g. due to horizontal and/or vertical misregistration of the component line portions contributed by the respective print/cartridges.
The problem of providing precise interrelation for a plurality of discrete orifice arrays is difficult, even in apparatus where the orifice arrays form relatively permanent parts of a printer. When the orifice arrays comprise portions of insertable print/cartridges the problem is even more difficult, for the print/cartridges should be inexpensive, dictating a minimum of high tolerance construction features and low tolerance assembly.
Commonly assigned U.S. patent application Ser. No. 945,136, entitled "Ink Jet Printer for Cooperatively Printing With A Plurality of Insertable Print/Cartridges" and concurrently filed in the name of M. Piatt, discloses a unique and advantageous approach for precisely interrelating a plurality of insertable print/cartridges for cooperative printing in an ink jet printer. The approach described in that application combines: (i) a precise physical positioning of the orifice arrays of such print/cartridges in regard to their vertical relation with the print zone and (ii) information signal adjustments to compensate for different horizontal interrelations of the orifice arrays with respect to the print zone. By utilizing partial physical and partial electrical inter-referencing of the print/cartridges, the approach described by that application greatly simplifies system positioning structures. The approach allows multi-array printing, via insertable print/cartridges, to be both economical and visually attractive.